|Buddleja davidii (white flowered form)|
About 100 species, see text.
Buddleja, or Buddleia (pron.: //) commonly known as the butterfly bush is a genus comprising over 100 species of flowering plants endemic to Asia, Africa, and the Americas. The generic name bestowed by Linnaeus posthumously honoured the Reverend Adam Buddle (1662–1715), a botanist and rector in Essex, England, at the suggestion of Dr. William Houstoun. Houstoun sent the first plants to become known to science as buddleja (B. americana) to England from the Caribbean about 15 years after Buddle's death.
The botanic name has been the source of some confusion. By modern practice of botanical Latin, the spelling of a generic name made from 'Buddle' would be Buddleia, but Linnaeus in 1753 and 1754 spelled it Buddleja, with the long i between two vowels, common in early modern orthography. The International Code of Botanical Nomenclature has gradually changed to incorporate stricter rules about orthographic variants, and as of the 2006 edition requires (article 60, particularly 60.5) that Linnaeus' spelling should be followed in this case.
Of the approximately 100 species nearly all are shrubs <5 m (16 ft) tall, but a few qualify as trees, the largest reaching 30 m (98 ft). Both evergreen and deciduous species occur. The leaves are lanceolate in most species, and arranged in opposite pairs on the stems (alternate in one species, B. alternifolia); they range from 1–30 cm (0.39–12 in) long. The flowers are produced in dense panicles 10–50 cm (3.9–20 in) long; each individual flower is tubular, about 1 cm (0.39 in) long, with the corolla divided into four spreading lobes (petals), about 3–4 mm (0.12–0.16 in) across. Flower colour varies widely, with white, pink, red, purple, orange or yellow flowers produced by different species and cultivars; they are rich in nectar and often strongly scented. The fruit is a small capsule about 1 cm (0.39 in) long and 1–2 mm (0.039–0.079 in) diameter, containing numerous small seeds; in a few species (previously classified in the separate genus Nicodemia) the capsule is soft and fleshy, forming a berry.
The genus is endemic to four continents. Over 60 species are native throughout the warmer parts of the New World from the southern United States south to Chile, while many other species are found in the Old World, in Africa, and parts of Asia, but all are absent as natives from Europe and Australasia. The species are divided into three groups based on their floral type: those in the New World are mostly dioecious (occasionally hermaphrodite or trioecious), while those in the Old World are exclusively hermaphrodite with perfect flowers.
Cultivation and uses 
As garden shrubs Buddlejas are essentially 20th-century plants, with the exception of B. globosa which was introduced to Britain from southern Chile in 1774 and disseminated from the nursery of Lee and Kennedy, Hammersmith. Several species are popular garden plants, the species are commonly known as 'butterfly bushes' owing to their attractiveness to butterflies, and have become staples of the modern butterfly garden; they are also attractive to bees and moths. Some species of South American Buddleja have evolved long red flowers to attract hummingbirds as exclusive pollinators.
The most popular cultivated species is Buddleja davidii from central China, named for the French Basque missionary and naturalist Père Armand David. Other common garden species include the aforementioned B. globosa, grown for its strongly honey-scented orange globular inflorescences, and the weeping Buddleja alternifolia. Several interspecific hybrids have been made, notably B. 'Lochinch' (B. davidii × B. fallowiana) and B. × weyeriana (B. globosa × B. davidii), the latter a cross between a South American and an Asiatic species.
Some species commonly escape from the garden. B. davidii in particular is a great coloniser of dry open ground; in urban areas in the United Kingdom, it often self-sows on waste ground or old masonry, where it grows into a dense thicket, and is listed as an invasive species in many areas. It is frequently seen beside railway lines, on derelict factory sites and, in the aftermath of World War II, on urban bomb sites. This earned it the popular nickname of 'the bombsite plant' among people of the war-time generation.
Popular garden cultivars include 'Royal Red' (reddish-purple flowers), 'Black Knight' (very dark purple), 'Sungold' (golden yellow), and 'Pink Delight' (pink). In recent years, much breeding work has been undertaken to create more compact buddlejas, most recently the production of dwarf varieties such as 'Blue Chip' (Lo & Behold™) which reach no more than 2–3 ft (0.61–0.91 m) tall, and are also seed sterile, an important consideration in the USA where B. davidii and its cultivars are banned from many states owing to their invasiveness.
Buddleja collections 
In the UK, there are four NCCPG national collections held by:
- The Lavender Garden, Ashcroft Nurseries, Kingscote, Tetbury, Glos. GL8 8YF. Tel. 01453 860356 www.thelavenderg.co.uk
- Longstock Park Nursery, Longstock, Stockbridge, Hants. SO20 6EH. Tel. 01264 810894 www.longstocknursery.co.uk
- Paignton Zoo, Totnes Road, Paignton, Devon TQ4 7EU. Tel. 01803 697529 www.paigntonzoo.org.uk
- The Shapcott Barton Estate, East Knowstone, South Molton, Devon EX36 4EE. Tel. 01398 341664
List of Buddleja species 
The many species of Buddleja have been the subject of much taxonomic contention. The listing below includes the names, still prevalent in horticulture, of many former Asiatic species sunk by the late Anthonius Leeuwenberg as Buddleja crispa and adopted as such in the definitive Flora of China. 
Formerly placed here 
- Cephalanthus glabratus (Spreng.) K.Schum. (as B. glabrata Spreng.)
Monarch butterfly feeding on Buddleja davidii in Connecticut
List of Buddleja hybrids and cultivars 
A large number of hybrids and cultivars, predominantly of B. davidii, has been raised in nurseries on both sides of the Atlantic:
RHS Award of Garden Merit 
See also 
Asiatic and African species 
- Leeuwenberg, A. J. M. (1979) The Loganiaceae of Africa XVIII Buddleja L. II, Revision of the African & Asiatic species. Mededelingen Landbouwhogeschool Wageningen, Netherlands.
American species 
- Norman, E. (2000). Buddlejaceae. Flora Neotropica, Vol. 81. New York Botanical Garden, USA. ISSN 0071 - 5794
Cultivated species and cultivars 
- Stuart, D. (2006). Buddlejas. RHS Plant Collector Guide. Timber Press, Oregon, USA. ISBN 978-0-88192-688-0
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- "Genus Buddleja". Taxonomy. UniProt. Retrieved 2009-10-21.
- "Buddleja L.". TROPICOS. Missouri Botanical Garden. Retrieved 2009-10-21.
- "Genus Buddleja L.". Germplasm Resources Information Network. United States Department of Agriculture. 2006-04-20. Retrieved 2010-11-29.
- Sunset Western Garden Book, 1995:606–607; OED: "Buddleia"
- The pronunciation of the long i in Buddleja as j is a common modern error.
- Stevens, P.F. (2001 onwards), "Scrophulariaceae", Angiosperm Phylogeny Website
- Alice M. Coats, Garden Shrubs and Their Histories (1964) 1992, s.v. "Buddleia".
- "Buddleja". Integrated Taxonomic Information System. Retrieved 10 April 2010.
- "GRIN Species Records of Buddleja". Germplasm Resources Information Network. United States Department of Agriculture. Retrieved 2010-11-29.
- Norman, E. (2000). Buddlejaceae. Flora Neotropica, Vol. 81. New York Botanical Garden, USA.